docs(readme): update assistant roster, prompt layers, repo structure

- Update assistant lists (added Shawn, Watson, David, CASE, AWS SA; modified Scotty/Harper roles)
- Reflect new architecture layers: Tool Prompt Snippets and Shared Context
- Align repository structure diagram with current filesystem layout

docs/tools/argos.md

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+# Argos
+
+> Web search and page fetch.
+
+- **MCP server name:** `argos` (runs on `miranda.incus` in the lab)
+- **Prompt snippet:** [prompts/tools/argos.md](../../prompts/tools/argos.md)
+
+## What It Is
+
+Argos is the agent's window onto the outside world: web search and webpage fetching. Named for the many-eyed giant of Greek myth, fitting for something that watches everywhere.
+
+## What It's Good For
+
+- General web search ("how do I…", "what is…", "current state of…")
+- Fetching a specific URL when the agent already knows where to look
+- Documentation lookups for libraries, frameworks, APIs (though Context7 is often better for these)
+- CVE references, vendor status pages, upstream incident announcements
+- Quick reality checks — "did this thing actually ship", "is this service up"
+
+## What It's Not Good For
+
+- Library/framework documentation when **Context7** is configured — Context7 is purpose-built for that and returns better-structured results
+- Anything inside the Agathos lab — use Kernos, not Argos, for internal services
+- Deep research with many follow-up queries — the agent should delegate to a research subagent rather than burning its own context window on long Argos chains
+- Code search inside a known repo — use Gitea or GitHub MCP for repo-scoped lookups
+
+## Known Gotchas
+
+- **Quotes and operators matter** — Argos respects search-engine query syntax. Bad quoting → bad results.
+- **Cached pages can mislead.** If a page's "last updated" matters (e.g., status pages, release notes), confirm by checking the page itself, not just the search snippet.
+- **Rate limits exist.** Burning Argos on a tight loop will eventually get throttled.